THE EFFECT OF SMALL STRESSES ON THE KINETICS OF THE BAINITE TRANSFORMATION

Experiments have been conducted in which bainite is allowed to grow un der the influence of an externally applied stress of magnitude less th an the yield strength of austenite. By monitoring the transformation s trains along two orthogonal directions, it has been possible to demons trate that the stress in general accelerates the overall transformatio n kinetics, particularly at high transformation temperatures, where th e chemical driving force for transformation is relatively small. An ac celeration of transformation at temperatures just above the martensite start temperature has been confirmed, even in the absence of an exter nally applied stress. The results are interpreted in terms of the mech anism of the bainite transformation in steels.